TY - BOOK

T1 - Theory of sorption and electronic transport in amorphous polymers and single molecules

AU - Jay, Michael

PY - 2020

Y1 - 2020

N2 - This thesis describes a series of studies of the energetics, structure, sorption and electronic transport of polymers and single molecules at the nanoscale.The first of these relates to hypercrosslinked porous polymers, which areof technological and commercial interest for their ability to efficiently absorbmolecules in a wide range of contexts from pharmaceuticals to gas storage.I model a family of polymers synthesised by collaborators at the Universityof Strathclyde, which show very high uptake of polyaromatic hydrocarbon(PAH) molecules from solution and could potentially be used as a filtration material to remove these molecules from vehicle lubrication oils, wherethey are responsible for the build up of soot and the long term degradation of both oil and engine. Density functional theory calculations identifiedthe structural units of the polymers contributing most to sorption, and therelative binding strengths of several PAHs which correspond to the experimental trends. Molecular dynamics simulations of the polymer pores withPAH molecules in a heptane solution highlighted the significance of polymerflexibility and pore size in the sorption process.In the second I analyse the conductance of the first organically synthesizedsp-sp3hybridized porous carbon, OSPC-1. This new carbon shows electronconductivity, high porosity, the highest uptake of lithium ions of any carbonmaterial to-date, and the ability to inhibit dangerous lithium dendrite formation. It therefore has potential as an anode material for lithium-ion batterieswith high capacity, excellent rate capability, long cycle life, and potentialfor improved safety performance. Detailed simulation of the variation of theconductivity of this amorphous material versus length using a tight bindingmethodology showed that the measured conductance is consistent with aninelastic scattering length of the size of an OPSC-1 fragment.The third project is in the field of molecular electronics, where a crucialarea of research aims to identify molecular anchor groups to bind moleculesto electrodes. This study presents a series of oligo(phenylene-ethynylene)wires with one tetrapodal anchor and a phenyl or pyridyl head group. Thenew anchors are designed to bind strongly to gold surfaces without disruptingthe conductance pathway of the wires. Density functional theory was usedto simulate the structures of the molecules and the nature of their bindingto the Au surface. Quantum transport calculations provided insight into theconductance pathway through the molecules and confirmed the decouplingbetween surface binding and electronic coupling. This feature may enablethe inclusion in junctions of a wider range of functional groups, in particularthose with strong electronic coupling, but only weak physical binding.

AB - This thesis describes a series of studies of the energetics, structure, sorption and electronic transport of polymers and single molecules at the nanoscale.The first of these relates to hypercrosslinked porous polymers, which areof technological and commercial interest for their ability to efficiently absorbmolecules in a wide range of contexts from pharmaceuticals to gas storage.I model a family of polymers synthesised by collaborators at the Universityof Strathclyde, which show very high uptake of polyaromatic hydrocarbon(PAH) molecules from solution and could potentially be used as a filtration material to remove these molecules from vehicle lubrication oils, wherethey are responsible for the build up of soot and the long term degradation of both oil and engine. Density functional theory calculations identifiedthe structural units of the polymers contributing most to sorption, and therelative binding strengths of several PAHs which correspond to the experimental trends. Molecular dynamics simulations of the polymer pores withPAH molecules in a heptane solution highlighted the significance of polymerflexibility and pore size in the sorption process.In the second I analyse the conductance of the first organically synthesizedsp-sp3hybridized porous carbon, OSPC-1. This new carbon shows electronconductivity, high porosity, the highest uptake of lithium ions of any carbonmaterial to-date, and the ability to inhibit dangerous lithium dendrite formation. It therefore has potential as an anode material for lithium-ion batterieswith high capacity, excellent rate capability, long cycle life, and potentialfor improved safety performance. Detailed simulation of the variation of theconductivity of this amorphous material versus length using a tight bindingmethodology showed that the measured conductance is consistent with aninelastic scattering length of the size of an OPSC-1 fragment.The third project is in the field of molecular electronics, where a crucialarea of research aims to identify molecular anchor groups to bind moleculesto electrodes. This study presents a series of oligo(phenylene-ethynylene)wires with one tetrapodal anchor and a phenyl or pyridyl head group. Thenew anchors are designed to bind strongly to gold surfaces without disruptingthe conductance pathway of the wires. Density functional theory was usedto simulate the structures of the molecules and the nature of their bindingto the Au surface. Quantum transport calculations provided insight into theconductance pathway through the molecules and confirmed the decouplingbetween surface binding and electronic coupling. This feature may enablethe inclusion in junctions of a wider range of functional groups, in particularthose with strong electronic coupling, but only weak physical binding.

U2 - 10.17635/lancaster/thesis/995

DO - 10.17635/lancaster/thesis/995

M3 - Doctoral Thesis

PB - Lancaster University

ER -